SPRINGFIELD— Brian Fanion, a former Westfield Police detective, was sentenced to life in prison on March 22 after jurors found him guilty of first-degree murder for killing his wife at their Westfield home in May 2018.

The guilty verdict came after a nearly month-long trial in Hampden County Superior Court, with the prosecution and defense offering competing versions of what happened at about noon at the Fanions’ home on North Road in the Wyben community of Westfield on May 8, 2018, when Amy Fanion, age 51, was fatally shot in the head.

As the trial began in earnest after nearly three days spent empaneling a jury, the prosecution, led by Hampden County Assistant District Attorney Mary Sandstrom, began building the case that Brian Fanion, 59, was motivated to murder his wife because he had fallen in love with another woman and didn’t want to share with his wife the pension he earned after working more than three decades with the Westfield Police Department.

But for Sandstrom, the case involved more than just offering jurors the reason Brian Fanion wanted his wife dead. She had to prove beyond a reasonable doubt he was guilty by examining the physical evidence at the scene of the shooting.

Moments after Amy Fanion was shot while eating a peanut butter sandwich and sitting at their dining room table, her brother Eric Hanson came to the front door of the Fanions’ home.

Hansen testified Brian Fanion began screaming at him to come in the house. When Hansen walked to the bloody scene, Brian Fanion was kneeling over his wife, holding her hands.

Brian Fanion told Hansen that Amy Fanion had shot herself with his department-issue .45 caliber handgun after yelling at him that he “obviously didn’t want or need” her anymore.

And that set in motion Brian Fanion’s defense: his wife committed suicide, he told investigators that she had erupted in rage about an ongoing argument the couple was having about their future together once he retired.

But almost immediately, investigators began questioning Brian Fanion’s story that his wife committed suicide.

The primary reason was the lack of evidence typically found when someone commits suicide, like gunshot residue that includes, soot, stippling or the stellate or star-patterned torn skin around the wound.

State investigators also mapped the trajectory of the bullet fired in the Fanions’ dining room and learned it was fired at a downward angle, not the typical flat trajectory of a self-inflicted gunshot to the head.

The bullet entered Amy Fanion’s head just above her right ear and exited her left cheek.

The state medical examiner who performed the autopsy on Amy Fanion’s body could not determine conclusively her manner of her death, saying it could be either suicide or homicide, citing the lack of wound evidence.

Seeking to rebut the prosecution argument about the lack of gunshot wound evidence, the defense, led by Jeffrey Brown, called expert witnesses to testify that Amy Fanion’s thick hair, which was parted on the left side of her head with a mass of hair draped over the right side, had masked the wound evidence.

Her hair, the defense witnesses testified, was an “intermediate target,” which could mask the effect of a close- or loose-gunshot wound to the head.

Investigators also didn’t find what is called “back spatter” on the gun. Back spatter typically, but not always, occurs when a gun is fired at close range and as the bullet and associated gases enter a body — it, in a fraction of a second — creates a cavity and as the cavity collapses, blood, skin and tissue are blown back toward the gun.

Blood was found on the outside of the gun, but not where it is usually found when back spatter occurs — inside the muzzle. The blood found on the gun was believed to have been deposited when Hansen pick it up after the shooting.

Sandstrom also used the lack of gunshot wound evidence to argue the gun was held from a distance of at least 1 foot away from Amy Fanion’s head when it was fired.

Expert witnesses called by Brown testified that the lack of gunshot wound evidence couldn’t determine the range or distance from where the gun was fired.

The prosecution also introduced evidence about the presence of gunshot primer residue detected at the scene. The primer residue, which occurs when gases are formed by the explosive charge in the primer when a weapon is fired, was found on the hands of Brian and Amy Fanion.

That evidence was not unexpected, a State Police forensic scientist testified, because the primer residue settles on everything in the immediate area when a gun is fired.

Sandstrom also called the woman Brian Fanion was romantically involved with to testify.

The Pittsfield woman had met Brian Fanion on a church-sponsored trip to Mexico in December 2017.

After they met, at first the relationship was cordial, but over several months the two began to have feelings for one another. The pair exchanged over 5,000 text messages between when they first met until the day of shooting.

In those messages, they professed loving each other.

Amy Fanion’s sister testified that she spoke with Brian Fanion about a month after the shooting. Her sister testified that Brian Fanion told her he felt a stronger connection to the Pittsfield woman than he ever had with his wife.

When Brown cross-examined the Pittsfield woman, he framed the romance as two teenagers in love and that the woman had wanted Brian Fanion to woo her, which she said he did.

Sandstrom also pointed to internet searches Brian Fanion made in the months before the shooting.

A Massachusetts State Police computer technician retrieved all the searches from Brian Fanion’s work and personal computer.

The data retrieved showed Brian Fanion searching for information about splitting a retirement pension after a divorce, common household cleaners that are deadly, and on the day of shooting, a search for information from the State Police crime lab in Maynard and its forensic evidence collection services.

When Brown cross-examined the State Police computer technician, the tech acknowledged that while he could determine that Brian Fanion had searched those sites, specifically about the forensic collection services, there was no way of knowing if he read the information.

The defense also tried to characterize Amy Fanion as prone to anger. Family members and one friend of Amy Fanion’s testified that she was “tightly wound.” However, under questioning by Sandstrom, none could recall her ever threatening to harm herself, even when angry.

And the Fanions’ daughter testified that she and her mother discussed suicide prior to the shooting and Amy Fanion told her daughter it was a selfish act and only hurt those left behind.

During the trial, several members of Brian Fanion’s family and Amy Fanion’s family, the Hansens, attended every session.

Many members of both families believed Amy Fanion committed suicide, and immediately after Brian Fanion’s guilty verdict was read, gasped in stunned disbelief.

Outside the courtroom, members of both families comforted each other with many weeping and others openly crying.

Brian Fanion had been free on bail since February 2020. After the verdict was read, he was placed in handcuffs and led from the courtroom by trial court officers.